Water or sediment? Partitioning the role of water column and sediment chemistry as drivers of macroinvertebrate communities in an austral South African stream

Journal article

Authors / Editors

Wasserman, Ryan

Research Areas

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Publication Details

Author list: Dalu T, Wasserman RJ, Tonkin JD, Mwedzi T, Magoro ML, Weyl OLF

Publisher: ELSEVIER SCIENCE BV

Place: AMSTERDAM

Publication year: 2017

Journal acronym: SCI TOTAL ENVIRON

Volume number: 607

Start page: 317

End page: 325

Number of pages: 9

ISSN: 0048-9697

eISSN: 1879-1026

Languages: English-Great Britain (EN-GB)

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Abstract

Water pollution is a critical management issue, with many rivers and streams draining urban areas being polluted by the disposal of untreated solid waste and wastewater discharge, storm water and agricultural runoff. This has implications for biodiversity, and many rivers in the developing world are now considered compromised. We investigated benthic macroinvertebrate community structure and composition in relation to physico-chemical conditions of the water column and sediments. The study was conducted in an Austral catchment subject to both urban and agricultural pollutants in two different seasons. We assessed whether sediment characteristics were more important drivers of macroinvertebrate community composition than water column characteristics. We expected clear differences in macroinvertebrate community composition and in the associated community metrics due to distinct flow conditions between the two seasons. A combination of multivariate analyses (canonical correspondence analysis (CCA)) and biological indicator analysis were used to examine these patterns. Chironomidae was the most abundant family (>60%) in the upper mainstem river and stream sites. Stream sites were positively associated with CCA axis 2, being characterised by high turbidity and lower pH, salinity, phosphate concentration, channel width and canopy cover. Canopy cover, channel width, substrate embeddedness, phosphate concentration, pH, salinity and turbidity all had a significant effect on macroinvertebrate community composition. Using CCA variation partitioning, water quality was, however, a better predictor of benthic macroinvertebrate composition than sediment chemical conditions. Furthermore, our results suggest that seasonality had little effect on structuring benthic macroinvertebrate communities in this south-eastern zone of South Africa, despite clear changes in sediment chemistry. This likely reflects the relative lack of major variability in water chemistry compared to sediment chemistry between seasons and the relatively muted variability in precipitation between seasons than the more classic Austral temperate climates. (C) 2017 Elsevier B.V. All rights reserved.

Keywords

Biological indices, heavy metals, macroinvertebrates, sediment chemistry, Water chemistry, Water flow, Water pollution

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